Abstract:In order to master the influence of differential settlement on the quality of cast-in-place beam, the finite element software ABAQUS is used to simulate the stress and strain of the early age concrete beam members under different ages and different settlement conditions. The maximum allowable difference in the quality of cast-in-situ beam in prefabricated soft foundation is given. The results show thatwhen concrete is subjected to excessive uneven displacement load in its early age, plastic zone will appear the cast-in-place beams, which will cause great harm to the quality of prefabricated beams. When the ultimate compressive strain is used as the criterion, the maximum uneven settlement of the structure is 12mm at 1 day, and it is 14mm after 2 days, 14 mm after 3 days, 15 mm after 7days. The maximum uneven settlement at 28 days is 17mm. Therefore, the quality of cast-in-place beams caused by differential settlement of soft soil can be effectively controlled by foundation treatment before the construction of prefabricated beams.

Abstract:Taking the high-grade K21 segmental rock slope in Zixing Expressway as the research object, a numerical model is built on the typical slope in the study area to simulate the excavation and supporting process of the slope by using on-site investigations, numerical simulation methods. Its stability, displacement, stress and strain features under different excavation and supporting are analyzed and summarized. The rationality of the excavation and support design and the safety of the slope reinforcement are verified. The stress-strain laws of the slope in the excavation and support process are analyzed. The results show that the main manifestation of disturbance in excavation of bedding rock slope is that the excavation destroys the original stress distribution of the slope, causes cracks and deformations in the rock mass and gradually expands, and weakens the strength of the rock and its stratum. Simultaneously, the open-cut cutting of the rock slope produces a free surface and directly destroys the original continuous force system of the slope. Due to the low shear strength of the weak layer, the overall rock formations slide along the weak structural surface which exposed by slope excavation. On one hand, the anchor cable frame increases the stability of the slope by controlling the displacement of the slope body. On the other hand, the layered rock mass is anchored together by the prestressed anchor cable, so that the frictional resistance between the layers increases. The stress and deflection are greatly reduced, which improves the shear strength of the layer greatly.

Abstract:There are many uncertainties affecting the stability of the foundation pit, such as the size of the foundation pit, the soil properties of the site, construction quality, and environmental factors. In order to explore a scientific and rational method for evaluating the stability of foundation pit slopes, based on the unascertained measure theory, this paper selects the depth of foundation pits, supporting methods, main soil layer cohesion, main soil internal friction angle, groundwater and surface, water effect, adjacent load, adjacent load pit margin, and construction quality as evaluation indicators. The weight of each index is determined by using the three-scale method combined with the analytic hierarchy process.The stability evaluation model of the foundation pit is established. This model is applied to two examples of foundation pit engineering. Compared with actual monitoring results, the reliability of evaluation results is credible. The results show that the foundation slope stability evaluation model based on unascertained measurement theory is feasible.

Abstract:The rolling stone disaster will directly affect the use of the bridge structure in the mountainous area, and even lead to the deviation of the bridge pier, the falling beam and even the collapse of the entire bridge. In order to simulate the dynamic process of rock-rock impact piers more realistically, this paper combines engineering examples to establish a finite element model, and introduces the theory of collision dynamics analysis and the principle of numerical analysis. The LS-DYNA is used to analyze the structural dynamic response of different rolling stone quality and different rolling stone speeds. The research shows that the greater the mass of the rolling stone and the higher the speed, the more significant the impact on the pier damage.

Abstract:Horizontal reinforcement of the slopes is one of the most widely used reinforcement methods. In this paper, the stability of the new-type reinforced soil slope is analyzed by morgensternprice horizontal bar division method, and the expressions of safety coefficient Fs and proportionality coefficient divisor are derived respectively according to the balance of bar force and moment, and the calculation results are obtained by iteration. Through the comparison and analysis of the numerical examples of horizontal slitting and horizontal Sweden method, the feasibility of this method is proved, which provides theoretical reference for reinforcement technology of slope engineering.

Abstract:In order to study the bond-slip performance between brick-rich recycled concrete and steel bars, 48 brick-rich cube specimens were tested through pull-out test. The effects of the cube compressive strength of recycled concrete, the shape of steel bar and the reinforcement diameter on the bond performance were studied. The results show the greater the strength value of recycled concrete, the larger the load value corresponding to the unit slip value, and the steeper the load-slip curve; when the strength and the reinforcement diameter are constant, the bonding stress of deformed steel bar (HRB400 grade steel) is about 1.55-1.75 times of Light round bar (HPB300). Lastly, through detecting damage by ultrasound, the bond-slip constitutive model considering damage between recycled concrete and steel bars was proposed.

Abstract:In order to study the compressive properties of brick-enriched recycled concrete at different water content rates, 72 blocks of RC20, RC25, RC30 enriched with brick recycled concrete cube standard maintenance 28d were transferred to the drying box for drying. treatment. The dried cube blocks were soaked in clear water 4h, 12h, 24h, 48h, 72h, 168h, and 336h respectively, and their moisture content was measured and the uniaxial pressure resistance mechanical properties were tested. The influence of water content on the compressive strength of recycled concrete was studied by experiment. The results show that the compressive strength of brick-rich recycled concrete decreases with increasing moisture content. For RC20, RC25 and RC30, the compressive strength of saturated brickrich recycled concrete cube decreases by 33.3%, 16.9%, and 36.9% respectively.

Abstract:Two grading scale methods in the Chinese standard, exclusion method and hybrid method, are used to scale a kind of coarse aggregate. Triaxial consolidation drainage shear tests have been performed on samples of different particle sizes. The results show that when the confining pressure is the same, the peak stress (σ₁-σ₃)_f and friction angle φ obtained by the exclusion method are higher than that obtained by the hybrid method. Coarse-grained material acquired by the exclusion method has a stronger dilatancy. Besides, under the same confining pressure, compared with coarse-grained material obtained by the hybrid method, both ε_af and ε_v0 obtained by the exclusion method are smaller and its M₀ is higher. Lastly, under the same particle size, the secant elastic modulus obtained by the exclusion method is about 1.03 to 1.39 times higher than that obtained by the hybrid method. When the particle size increases, the bulk modulus obtained by the exclusion method increases less than that obtained by the hybrid method and the elastic modulus parameter K obtained by the two scale methods increases and the deformation modulus index n decreases.

Abstract:Recycled aggregate concrete is prepared by using waste concrete processing as regenerated fine aggregate, and three kinds of water-to-binder ratio are arranged with variable rate of regeneration fine aggregate replacement. The influence of aggregate replacement rate on the elastic modulus of brickrich recycled concrete and the relationship between ultrasonic wave velocity and elastic modulus are investigated through concrete standard elastic modulus test method, constitutive relationship test method and ultrasonic non-destructive testing. The results show the slope of the secant of the rising section of the stress-strain curve is the same as the variation of the elastic modulus of the recycled concrete with the change rate of the regenerated fine aggregate, which is consistent with the change of the elastic modulus test. When the replacement rate is 30%, the best condition is achieved. The calculation model of the relationship between compressive strength and elastic modulus of brick-recycled concrete cubes is proposed by taking the replacement rate of recycled fine aggregates as the influencing factors, and the ultrasonic wave velocity and the elastic modulus of recycled concrete are fitted.

Abstract:Drilling exploration show that the construction area is complex. There are a lot of pebbles and other hard rock, which will have a great impact on the jacking of the pipe jacking. It is necessary to formulate a suitable and effective construction site for the pipe jacking construction and reduce the probability of stuck drilling. The high-density electrical method exploration equipment is used to carry out detailed surveys of the strata in the construction area. Firstly, the fault layer near the construction area is measured, which proves the reliability of high-density electric method technology in the exploration of stratum distribution and rock formation. Finally, The Wenner device and the Schlumberger device are used to survey the proposed construction area and good results are achieved. Initially, a grounding depth trend with less obstacles is proposed for the pipe jacking construction.

Abstract:The technology of monoethanolamine(MEA) chemical absorption has high energy consumption in practical applications. Based on the analysis of the traditional MEA CO₂ capture technology, this paper proposes a novel MEA CO₂ capture technology that heat is provided by Fresneltype solar heat pump and coal fired unit gas heat recovery system. Based on the Aspen Plus software, the new MEA CO₂ capture process is simulated and the representative prediction results are obtained. The results show that the new MEA CO₂ capture process can save energy by 63.80%; the temperature distribution curve in tower of the new CO₂ capture system is smoother, which is more conducive to the rapid separation of CO₂.

Abstract:In this paper, a soil particle starting model based on the theory of sediment motion mechanics is established. Based on the relative exposure, the formula for calculating the critical velocity of internal erosion caused by soil seepage is derived. Comparing with the critical flow rate measured in the test, it is found that the test value is consistent with the calculated value. The difference between the calculated value of the critical flow rate and the experimental value and the relationship between the relative exposure and the critical flow rate are discussed. The accumulation of particles during the seepage process will cause the particle transport channel to block, and the critical flow rate test value is greater than the calculated value. The critical flow rate is positively correlated with the relative exposure of soil particles. The relative exposure degree has different influence on the critical flow rate in different seepage directions. The relative exposure has a great influence on horizontal seepage. For the vertical seepage, the relative exposure has little effect on the critical flow velocity.

Abstract:Based on random weight particle swarm optimization and least square support vector machine, the displacement inverse analysis model of mechanical parameters of underground cavern was established. The learning samples were determined by orthogonal test and 3DEC model. Using this model, the inverse analysis was carried out. The results show that the inverse analysis of mechanical parameters can be realized by using the nonlinear mapping of support vector machine method. The two lateral pressure coefficients are 0.453 and 0.644, and the elastic modulus of three kinds of rock masses are 10.15, 8.20 and 2.62 GPa. The deviation between the displacement obtained from inverse analysis and on-site measurement is small, which verifies the rationality of the inversion parameters.

Abstract:There are pores in the gangue of coal seam, and it has the ability of adsorbing gas. In order to study the pore characteristics of coalbed gangue in Xinjing Coal Mine of Qinshui Basin, the experimental study on static adsorption of liquid nitrogen was carried out by selecting gangue from seam 8# and gangue from seam 15#. According to the experimental results, the specific surface area, pore diameter ratio and aperture in the pore structure characteristics of gangue in No. 8# coal seam and No. 15# coal seam in Xinjing Coal Mine are analyzed. The results show that the gangue in Xinjing 8# coal seam is mainly composed of micropores and small holes, which account for more than 92% of the total holes. The gangue of Xinjing 15# coal seam is mainly composed of micro hole, small hole and middle hole. The proportion of micro hole and small hole is 67%, and that of middle hole is about 32%. The size of micropore and pore size has a strong correlation with the specific surface area and adsorption capacity.

Abstract:In order to study the influence degree of rainfall intensity on the instability of superficial slope, based on the detailed geological survey in the field, the Geostudio software is used to simulate the seepage field and stability of the slope under different rainfall conditions, and study the stability coefficient and instability probability under the corresponding working conditions. then, the risk assessment of the slope under extremely unstable conditions through the quantitative method is carried out. The results show that the slope is only vulnerable to instability under fully saturated conditions. The probability of instability is as high as 48.93%. The total value of the disaster-bearing body in the landslide-affected area is 3.619 million yuan, the annual loss of property is 0.8324 million yuan, and the probability of single-person annual death is 8.7^*10^-2, which is in the extremely high risk area.

Abstract:The Specific surface area and pore structure are two important characteristics of shale. The specific surface area has an important influence on the adsorption characteristics and expansibility of shale. When measuring the specific surface area of shale gas, the result of specific surface area of shales is not so precise because of a large number of micro-nano pores. Based on the relationship between the specific surface area and space structure, the mathematical model is established, and the relationship between the specific surface area and pore structure of shale is discussed with two parameters, the number ratio and volume ratio. Results show that the microporous for specific surface area has important contribution to the shale, and small specific surface area is positive correlation relationship with pore volume ratio. This paper provides a theoretical basis for the study of shale gas adsorption characteristics and shale expansion characteristics.

Abstract:When treating sand layer as a bearing layer, it is regarded as a non-cohesive soil with zero cohesion. This neglect of cohesive force is too low to estimate the strength of the soil, which may lead to relatively conservative design parameters and high engineering cost. In addition, when soil nailing is used in the foundation pit of the sand layer, the hole is not easy to form, and it is easy to collapse and cannot be properly constructed. By introducing the cohesive force of unsaturated sand, In this paper, the mechanical method is used to analyze the stability of the sand layer. The stress field and displacement field redistributed after the hole-forming are obtained., Based on the foundation pit support project of a building in Xi'an, the pore stability is analyzed by numerical simulation software Flac3D. The results show that the pore-forming property of sand-soil layer is related to the clay-like cohesive force. Under a certain degree of compactness, the cohesive force of sand is related to its water content. In the engineering practice, the soil nailing of the sand layer can be ensured by changing the moisture content of the sand.

Abstract:In order to study the acoustic emission (AE) characteristics of different layered angle and anchored rock deformation and failure process, the anchored samples of 0ånd 90° two layers were processed. The RMT-150C rock mechanic test machine and AEwin-USB AE signal acquisition system were used to test AE characteristics of the layered and anchored rock. The results show that under the condition of uniaxial compression, the AE cumulative ringing count of the 90° layered sample is greater than 0° layered sample, and it has a significant bedding effect. Compared with non-anchored sample, anchored sample have stronger AE signals during compaction stage, and the AE signals become stronger as the load increases. The cumulative ringing count of anchored sample is also greater than nonanchored sample. The characteristics of AE signals can reflect the variation of crack propagation inside the rock, which has certain reference value for revealing the failure mechanism of layered and anchored surrounding rock.

Abstract:Taking samples of different depths of Q₃ loess at the exploratory well of Heping Town in Lanzhou, the particle analysis was made in the laboratory. The conventional physical and mechanical indexes were measured, as well as the coefficient of collapsibility of soil samples with different depths. The collapsibility of loess in this area is mainly medium and weak collapsibility, and a small amount of loess is collapsible. The peak of collapsibility coefficient decreases gradually with the increase of depth, and the sensitivity of collapsibility is general. The sandy loess with different depths will show different collapsibility under different pressures. As the Loess horizon deepens, the influence of upper load on Collapsibility gradually decreases. Under the same pressure, the collapsibility coefficient of the upper and middle loess is larger, and the collapsibility coefficient of the lower loess is smaller.

Abstract:Through the investigation and analysis of 104 unstable slopes in Zhashui County, it is found that the stacked unstable slope is the main slope in the area. The original slopes range is 30~45 degrees, which is most favorable to the development of unstable slopes, and the original height interval which is most conducive to the development of unstable slope is 50~100 m. Due to the weakening of human engineering activities, the development of unstable slopes is reduced in high-steep slopes with original slopes greater than 45° and slope heights greater than 100 m. The deformation and failure modes of unstable slopes are mainly divided into three categories:slip-cracking pattern, slip-compression cracking pattern and bending-cracking pattern and slip-cracking pattern is the most common pattern.

Abstract:In the light of the problem of gas extraction and disaster control for coal mining face with high gas and low permeability, No.15311 fully-mechanized face of Tucheng Mine was considered as an object of study in this paper. Firstly, the source of gas emission was preliminarily analyzed, the different-source prediction method was applied to predict the gas emission. Secondly, several methods of gas extraction, such as in-seam boreholes in mining seam, boreholes through mining seam in bed plate tunnel, boreholes in the high level gateway, and the pipeline buried in the goaf, was used to put forward the 3D prevention and control technology for gas combining with the ventilation in coal mining face. Basic on it, the spillover gas was intercepted and pulled out by drilling construction in the roadway floor, and the effect of extraction is also investigated. The filed practice indicated that:the source of gas emission in No.15311 fully-mechanized face is mainly form the coal seam and the lower adjacent layer, total gas extraction is 45.4 m³/t, gas extraction rate is 85.33%, the concentration of gas has not exceeded 1% in return air, this effectively control coal mining face of gas emission source.

Abstract:Sensor-based human activity recognition (HAR) has important research value and significance in the field of health care. Previous researches on classification and recognition of sensor human activities have not considered the imbalance between different categories of behavior data. In order to solve the problem that the imbalance between data of different behavioral categories affects the accuracy of the algorithm, our algorithm uses the downsampling method to randomly extract two sets of data from large and small data sets, which are equal in number, and transform multiple imbalanced data into balanced data. Secondly, multiple weak classifiers are trained on multiple balanced datasets. Then, the algorithm takes the negative correlation and prediction accuracy of the weak classifier as the cost function and uses genetic algorithm to select the weak classifier which can make the highest value of the cost function to form the integrated classifier. The weak learner in the ensemble algorithm has high prediction accuracy and diversity. Finally, the algorithm uses the selected weak learners to construct an ensemble learner to classify human behavior. The experimental results show that the proposed algorithm can effectively improve the accuracy of unbalanced behavior recognition compared with the traditional algorithms.

Abstract:This paper expounds that the element part belongs to the virtual fuzziness presented by the fuzzy set, why not be the object of the fuzziness research, why the fuzzy set theory taking the virtual fuzziness as the research object is not successful and the negative impact on the normal fuzziness research. It is pointed out that the fuzziness to be studied has incomplete and imperfect information, and the "truth value" of the target value can not be known that only the uncertainty generated by the approximation of the truth value can be determined. In the fuzziness study, a supporting logic should be established to help solve the problem of non-repeatability of calculation, non-unique calculation results and not "relative optimal approximation" in the fuzziness study. The most qualitative point is to solve the problem of "algorithm realization" of knowledge transformation under the relevant relationship, which is the key point of whether the fuzziness research can succeed and whether the fuzziness research can become the branch of mathematics research like the randomness research.